The field of the present invention is air driven reciprocating devices.
Pumps having double diaphragms driven by compressed air directed through an actuator valve are well known. Reference is made to U.S. Pat. Nos. 5,213,485; 5,169,296; and 4,247,264; and to U.S. Pat. Nos. Des. 294,946; 294,947; and 275,858. Actuator valves using a feedback control system are disclosed in U.S. Pat. Nos. 4,242,941 and 4,549,467. The disclosures of the foregoing patents are incorporated herein by reference.
Common to the aforementioned patents on air driven diaphragm pumps is the disclosure of two opposed pumping cavities. The pumping cavities each include a pump chamber housing, an air chamber housing and a diaphragm extending fully across the pumping cavity defined by these two housings. Each pump chamber housing includes an inlet check valve and an outlet check valve. A common shaft typically extends into each air chamber housing to attach to the diaphragms therein.
An actuator valve receives a supply of pressurized air and operates through a feedback control system to alternately pressurize and vent the air chamber side of each pumping cavity through a control valve piston. Feedback to the control valve piston has been provided by the position of the diaphragms. This may be through the shaft attached to the diaphragms which includes one or more passages to alternately vent the ends of the valve cylinder within which the control valve piston reciprocates. Alternatively, relief valves may include actuators extending into the path of the diaphragm assembly such as disclosed in U.S. Pat. No. 5,927,954, the disclosure of which is incorporated herein by reference. By selectively venting one end or the other of the cylinder, the energy stored in the form of compressed air at the unvented end of the cylinder acts to drive the piston to the alternate end of its stroke.
The use of air driven diaphragm pumps has expanded in recent years. Use of the pumps in chemically reactive applications and ultra-clean applications has put stringent requirements on such pumps regarding materials and safety features. High temperature applications provide further issues with regard to design and material selection.